1. Field of the Invention
The present invention relates generally to an electrochemical biosensor and, more particularly, to a method for determining the electrochemical characteristics associated with a biosensor test strip.
2. Description of the Related Art
Diabetic patients routinely use over-the-counter blood glucose meters to measure their blood glucose levels. First, the patient inserts a blood glucose test strip into its associated blood glucose meter. Then, the patient places a drop of blood sample over the test strip, causing the blood sample to react with an enzyme reagent, which is placed on the reaction zone over the working electrode and the reference electrode. At this time, by applying a fixed or variable electric potential across the reaction zone, the blood glucose meter may calculate the blood glucose level based on the electrochemical characteristics generated from the measured voltage or current.
The accuracy of the blood glucose reading, however, depends on several factors, some of which are difficult to control. For example, the accuracy depends on the materials used in the test strips. In particular, the accuracy depends on the surface properties of the working and the reference electrodes, which tend to vary among individual test strips. Moreover, some electrochemical characteristics of the enzyme reagents are highly susceptible to manufacturing and environmental variables. These variables may negatively affect, for example, the number and sizes of the air bubbles present in the enzyme reagent and hence the homogeneous distribution of the enzyme and mediator, such as potassium ferricyanide. These variables may also negatively affect the coverage completeness of the enzyme reagent over the reaction zone. All of these may cause significant differences in the performance among test strips under the same testing conditions. Accounting for, but not limited to, the above problems, manufacturers often assign batch-specific codes to the test strips to account for the variability among each batch. This practice, however, increases the production cost and makes the glucose monitoring system less user-friendly.
Since physicians often refer to blood glucose readings as an aid to monitor the effectiveness of diabetes management and to give appropriate medical treatments, the accuracy of the readings is very critical. Accordingly, at the end of the manufacturing processes of the test strips, usually a number of test strips are randomly selected from a manufacturing batch to test for their conformity with the specification. This sampling method, however, cannot guarantee the quality of the entire batch of test strips, and cannot remove the defective test strips, if present, in the batch. Moreover, because the quality assurance test conducted on a selected test strip is usually destructive and non-reversible, the selected test strip loses its value after the test. This in turn increases the cost of sampling, and limits the number of test strips available for sale. Therefore, there is a need in the art to provide an accurate and non-destructive method to assure the quality of a biosensor test strip.